Conventionally, an aluminum tube having a surface roughness Ry of an outer surface being around 1.0 to 3.0 μm has been manufactured by, for example, subjecting an aluminum raw material (e.g., aluminum billet) to extrusion processing and drawing processing in this order. Such a drawn tube is called an “ED (Extrusion Drawing) tube.” Such a drawn tube is used as, e.g., a photoconductive drum substrate for electrophotographic devices (e.g., copying machines, laser beam printers).
Japanese Unexamined Laid-open Patent Application Publication No. 2005-118799 (JP-A-2005-118799, hereinafter referred to as “Patent Document 1”) discloses a drawing processing device (diameter-reducing processing device) equipped with a drawing die for reducing an outer diameter of a metal tube as a tubular workpiece (see Patent Document 1). This drawing processing device is not equipped with a drawing plug for processing an inner surface of a tube, which employs an empty drawing method. Therefore, the device is characterized in that the drawing processing causes an increase of a wall thickness of the tube. The purpose of this drawing processing device is to prevent an increase of the wall thickness of the tube without using a drawing plug and to prevent occurrence of chattering marks on an outer surface of the tube during the drawing processing.
Japanese Unexamined Laid-open Patent Application Publication No. H08-66715 (JP-A-H08-66715, hereinafter referred to as “Patent Document 2”) discloses a method of producing a solid-core wire or rod, not a tubular member, by drawing processing. The workpiece used in this method is not a tubular member but a solid-core member. Therefore, the drawing processing device used in this method is not required to equip a drawing plug.